Forked contact and method of manufacture



A ril 30, 1968 E. E. GEHRT ETAL 3,381,253

FQRKED CONTACT AND METHOD OF MANUFACTURE Original Filed March 20, 1961ATTORNEYS United States Patent 1 Claim. or. 339-477 ABSTRACT OF THEDISCLOSURE A bifurcated electrical contact of the type adapted to matewith an identical contact to establish positive electrical connectionbetween two components is formed of sheet metal stock of uniformthickness and the legs of the bifurcation are swaged to provide opposedcontact surfaces which conform substantially to the section of acylinder of uniform diameter to facilitate mating and unmating whilemaintaining positive electric contact in the mated position.

This application is a division of our earlier application Serial vNo.381,285 filed June 25, 1964, now U.S-. Patent No. 3,299,493 and thelatter is a continuation of our earlier application Serial No. 96,947,filed March 20, 1961, now abandoned.

This invention is concerned with contacts for use in forming electricalconnectors. The contact is of the bifurcated or forked type where twocontacts of identical construction are engaged with their prongs incontact with each other to form a connector. The prongs of each contactfunction both as a socket and as a prong for the opposing contact.

Contacts of this type are useful for many purposes, one example beinguse on printed circuit boards as shown in US. patent to Blain 2,946,976where a set of forked contacts are mounted on the board and another setof contacts are carried by a suitable base or support and oriented toengage the first set. If the inner edge faces of the prongs are formedof flat areas joined along sharp corners, such corners are likely toprevent smooth sliding engagement of two contact pieces, especially ifthe two pieces are not mounted with their planes exactly at right anglesto each other, or if one contact piece is cocked with respect to theother.

An object of the invention is to devise a forked contact of novelstructure which will provide for smoother mating of the prongs of a pairof contacts when placed into mating relation.

A specific object is to devise a forked contact in which the surfaces ofthe inner edges of the prongs of the contact are rounded to conformsubstantially with a cylindrical surface. In the preferred embodimentthe inner edge portions of the prongs are formed as rounded beadportions extending along the active length of each prong.

A further object of the invention is to devise a novel method of formingthe improved contact, involving the use of swaging dies to form thebeaded edges on the contact prongs.

The invention is illustrated in the accompanying drawing in which:

FIGURE 1 shows a plan view of the novel contact;

FIGURE 2 is a view of a section of FIGURE 1 taken along the transverseplane 2-2 of FIGURE 1;

FIGURE 3 is a plan view on a smaller scale than FIG- URE 1 showing astrip of metal from which the contact is formed and showing variousstages in the formation of the contact;

FIGURE 4 is a sectional view on a greatly enlarged scale showing asection of FIGURE 3 taken along the cutting plane 4-4 of FIGURE 3 andshowing the swaging dies forming the beaded edge portions; and

FIGURE 5 is a transverse sectional view on a greatly enlarged scaleshowing portions of two contacts arranged in mating relation.

Referring to the drawing, FIGURE 1 shows a plan view of the contactformed from a flat strip of metal. The scale of FIGURES 1 and 2 isconsiderably enlarged for contacts which would be used on printedcircuit panels. The contact is provided with a shank portion 1 havingsuitable mounting ears 2 and 3 extending from one edge thereof. In thedrawing these cars extend rearwardly from the rear end of the shankportion, but they might extend from one of the side edges of the shankportion. At the forward end of the shank portion two prongs 4- and 5extend forwardly in parallel relation and are separated by a slot or gap6 which terminates at its rear end in an enlarged opening 7 which, forconvenience in producing the necessary die parts, is of circular outlinebut could be triangular or of other shape.

As shown in FIGURE 2, the inner or facing edge portions 4a and 5a of theprongs 4 and 5 on opposite sides of the slot 6 have a rounded surfaceconforming substantially to a cylindrical surface extending over acircular arc of more than that is, more than 45 on each side of thecommon plane of the two prongs. In the particular construction shown thecylindrical surface of the inner edge portions 4a and 5a of the prongextend over a circular arc of substantially 270.

The inner edges of prongs 4 and 5 at the ends thereof are tapered orflared outwardly as shown at 4b and 5b to provide converging surfaces atthe entrance to slot 6 to facilitate proper mating when two forkedcontacts are being moved into mating relation.

The manner of forming the contact from a strip of sheet metal,preferably spring tempered Phosphor bronze, is as .follows:

It will be understood that the metal strip 8 is fed stepby-step into asuitable punch-press which is provided with suitable punch and die toolsat different stations or locations, the strip 8 traveling from right toleft as shown in FIGURE 3. The strip is properly indexed or piloted inthe different stations by a series of pilot holes 9 formed by a punch atone location. At the first station, a suitable punch and die forms thetriangular perforation 10 having its broad side parallel with one edgeof the strip 8 and the apex directed towards the opposite edge. The apexsides of perforation 10 form the tapered edges 4b and 5b for prongs 4and 5 which are punched out at a later station. It is preferred that theedges 4b and 5b be at right angles to each other. At the second stationa punch forms the enlarged hole 7. At the third station a narrow punchcuts a narrow slot 6 through the strip and connecting the holes 7 and10. At this point slot 6 has a Width less than the thickness of thestrip 8 and is slightly wider than in its final form, to allow for acertain narrowing of the slot by the swaging operation.

At the fourth station a pair of swaging dies of the forms shown at 11and 12 in FIGURE 4 engage the edge portions of the slot walls, bothabove and below the strip, to form the bead portions 4a and 5a extendingalong the inner edges of prongs 4 and 5, respectively. This swagingoperation causes cold flow of the edge portions of strip 8 and shapesthese portions into bead strips of round section as shown in FIGURES 2and 4. The forming surfaces of dies 11 and 12 conform substantially withcylindrical surfaces having axes located in the mid-plane of strip 8 andhaving a radius equal to or somewhat less than half the thickness of thestrip. The metal flow during swaging also effects some closing of theslot 6 to its proper width. The dotted lines in FIG- UR-E 4 show theshape of the edge portions of the prongs before the swaging or coiningoperation. The pointed rib-portions 11a, 11b and 12a and 12b bite intostrip 8 and cause a certain fiow of metal towards the center of the diewithout imposing substantial spreading action on the two prongs. Theserib portions of die members 11 and 12 serve to hold the prongs againstoutward displacement laterally of the slot 6 while the rounded portionsof die members 11 and 12 are squeezing or coining the inner edgeportions of the two prongs into rounded bead form.

At the fifth station a 'blanking die having the shape of the outline ofthe contact piece blanks the completed contact piece from the strip 8and leaves the perforation 13.

FIGURE shows the rounded edge portions of the prongs engage each otherwhen two contact pieces are placed into mating relation, prongs 4 and 5being on one piece and prongs 4 and 5 on the other piece.

It is desirable that each contact piece be formed so that the gapbetween the prongs at the end portions is of a width slightly less thannear the shank, so that the prongs of each piece will exert a grippingaction on the prongs of the other piece when two pieces are in matingengagement.

We claim:

1. A bifurcated contact formed of sheet metal of uniform thicknesscomprising a shank portion and two prong portions formed integrally withsaid shank portion and extending in parallel relation from said shankportion, said prongs being separated by a narrow gap of a width lessthan the thickness of the prongs, each of said prongs havinglongitudinal grooves formed in opposite faces thereof and adjacent saidgap to define an edge portion adjacent said gap of a width substantiallyless than the width of the remaining or outer longitudinal portion ofthe prong, and the edge portions of said prongs defining opposite sidesof said gap being of a rounded sectional form presenting outer surfacesconforming substantially to cylindrical surfaces extending on oppositesides of the common central plane of said prongs to an arcuate extent ofmore than on each side of said plane.

References Cited UNITED STATES PATENTS 2,377,558 6/1945 Johnson 78-602,828,474 3/1958 Fox 339-47 3,070,769 12/ 1962 Murphy 339-49 FOREIGNPATENTS 20,685 1898 Great Britain. 4,974 1905 Great Britain.

MARVIN A. CHAMPION, Primary Examiner.

P. TEITELBAUM, Assistant Examiner.

